Masiello started his career at Venezia, he made one Serie B appearance before moving to Lumezzane (Lega Pro Prima Divisione). In January 2003, he was signed by U.S. Città di Palermo and rejoined chairman Maurizio Zamparini. In the 2004–05 season, he became a surplus of newly promoted Palermo, and he was loaned to Piacenza along with Simone Pepe. In the 2005–06 season, he returned to Palermo, and made his Serie A debut on 6 November 2005, against Sampdoria.
In January 2006, he was involved in the transfer deal of David Di Michele, to join Udinese along with Pepe and Nicola Santoni in joint-ownership.[1] Masiello's half-registration rights were valued at €250,000 at that time.[2] In the 2005–06 season, he played three Serie A games, two for Palermo and one for Udinese.
In the 2006–07 season, he was loaned to Messina (Serie A) and in 2007–08 for Vicenza (Serie B). In June 2008, Udinese acquired the whole rights for free.[3]
In the summer of 2008, Masiello joined AS Bari from Udinese by joint-ownership bid, for €200,000.[4] In June 2011, Bari acquired Masiello outright and sold Paulo Vitor Barreto back to Udinese.
Press reports in August 2011 stated that he was involved in a plate-throwing incident at a Bari team dinner. Fellow Bari player Alessandro Crescenzi was reportedly struck by the plate and had to have 40 stitches in the resulting wound. The club announced its intention to refer Masiello's conduct to the Court of Sports Arbitration of Lega Serie B and to seek the termination of Masiello's contract.[5][6]
On 31 January 2012, the last day of the transfer market, he moved to Torino, with whom he signed a contract until 2013. At the end of the season, he was promoted to Serie A, playing only the last league game AlbinoLeffe - Torino (0–0).
The following season competed in the top division with the Granata, he totaled 24 appearances. He remained a free transfer at the end of the season, but on 8 July 2013 signed a new contract with the Granata. He followed the same fate the following year: left without a contract, he signed with Torino for another season.